1. Field of the Invention
The present invention pertains to a mud containment apparatus, frequently referred to as a “mud bucket”, for preventing fluid from uncontrolled spillage when joined sections of pipe are separated on a drilling rig. More particularly, the present invention pertains to a mud containment assembly that can be quickly and efficiently positioned around connected sections pipe, and that contains and collects fluids (such as, for example, drilling mud and/or additives) when said pipe sections are separated. More particularly still, the present invention pertains to a mud containment apparatus that comprises a plurality of fluid pressure sealing members that can be selectively energized for engagement against said pipe.
2. Brief Description of the Prior Art
Drilling rigs typically comprise a supportive rig floor, a derrick that extends in a relatively vertical direction above said rig floor, and a lifting device that can be raised and lowered within said derrick. Generally, a wellbore is positioned beneath said rig floor and derrick and extends in a relatively downward direction into subterranean strata. During drilling operations, said drilling rig and associated equipment can, among other things, be used to move tubular goods, such as drill pipe, casing and/or other tubulars, into and out of said wellbore.
Frequently, boring drill bits and/or other equipment can be lowered into a wellbore and manipulated within said wellbore via a tubular work string. For example, oil and gas wells are generally drilled by rotating a boring bit located at the distal end of a length of a tubular drill string; said drill string comprises a plurality of individual joints of drill pipe that are threadably and coaxially connected to one another in end-to-end relationship.
A fluid, generally known as drilling mud or drilling fluid, is often pumped into a through-bore of such drill pipe during the drilling process. Said drilling mud is circulated back to the drilling rig through an annulus formed between the outer surface of said drill pipe and the inner surface of the wellbore. After exiting said wellbore annulus, the drilling mud is directed into a plurality of mud tanks that are beneficially located on or near the drilling rig. Such circulated drilling mud can then be filtered and cleaned before being pumped back through the through-bore of the drill pipe and re-circulated through said wellbore.
Drilling mud can serve several purposes. For example, such drilling mud can be used to provide a hydrostatic head to offset downhole fluid pressures observed in a wellbore; the density of the drilling mud can be adjusted using weighting material and/or additives in order to provide a desired hydrostatic head. Drilling mud can also be used to lubricate and cool a downhole drill bit, and to carry drilled rock cuttings or pieces to the surface. Additives and chemicals are frequently added to drilling mud in order to provide or adjust the various characteristics and/or performance of such drilling mud.
Drilling mud, with or without additives, can be harmful to rig personnel. Exposure to said drilling muds and/or additives can frequently cause allergic skin reactions and other health problems. Additionally, said drilling mud and additives can be environmentally hazardous and extremely expensive. As a result, it is virtually always desirable to contain said drilling fluids and to prevent said drilling fluids from splashing, spilling and/or otherwise contacting personnel and drilling rig equipment that is not part of the mud system.
When removing a string of pipe from a wellbore (such as, for example, in order to remove and change a drill bit located at the bottom or distal end of the drill string)—a process often referred to as “tripping out of the hole”—pipe is removed from the well one or more sections at a time. During such tripping, the upper end of the drill string is lifted within a drilling rig derrick until a threaded connection between two joints of drill pipe is positioned a relatively short distance above a rig floor. Thereafter, the pipe string is suspended or hung in place at the rig floor using a device commonly known as “slips”.
After the slips have been set and the pipe is secured in place within the wellbore said threaded connection can then be “broken-out” or loosened by tongs or other torque application means. After said threaded connection is broken out, the uppermost (now disconnected) section(s) of pipe can be completely unscrewed, removed from the drill string and stored within the derrick or on a pipe rack, and the process can be repeated until a desired length of pipe is removed from said wellbore.
In many cases, drill pipe lifted within a drilling rig derrick is at least partially filled with drilling mud. As a result, a considerable volume of drilling mud contained within said pipe can spill and/or splash onto the rig floor following unscrewing of said threaded connection and separation of two adjacent pipe sections above said rig floor. Such drilling mud can splash on personnel and get into their eyes or come in contact with their skin; the drilling mud can also spill off of the rig floor and into the surrounding environment. Drilling mud on a rig floor or other surfaces can create a slipping hazard to rig personnel. Expensive drilling mud lost in this manner must then be replaced instead of being re-used.
Attempts have been made to solve the problem of controlling the spilling of drilling fluids during separation of a threaded connection using a device commonly referred to as “mud bucket”. Generally, such mud buckets comprise a substantially cylindrical-shaped container fabricated by splitting or cutting a length of a relatively large diameter pipe along a mid-plane through its longitudinal axis, thereby creating two substantially semi-cylindrical halves of roughly equal size. Said two halves of said cylinder are hinged along one long side and include a latching or locking mechanism opposite said hinge.
An elastomer sealing member is disposed in a relatively horizontal configuration at both the upper and lower ends of said cylinder, while an elastomer strip seal is disposed in a relatively vertical configuration between said two halves of said cylinder. Further, an opening at the bottom end of one of the cylinder halves permits fluids received in an inner volume of the mud bucket to evacuate to a mud tank or other drilling mud reservoir via a hose.
During operation, the opposing semi-cylindrical half members of a mud bucket may be hinged open or spread apart. In this configuration, said mud bucket is placed in close proximity to a mated threaded connection between two adjacent sections of pipe positioned above a drilling rig floor. Said opposing semi-cylindrical half members can then be closed against each other (using said hinge) in order to envelop said threaded connection and a portion of the surrounding drill pipe. Thereafter, the mud bucket may be latched in order to surround said threaded connection and secure said opposing semi-cylindrical members in a closed or joined relationship.
Upper and lower elastomer sealing members located near the upper and lower ends of said opposing semi-cylindrical half members have substantially semi-circular or concave sealing surfaces. Said concave upper elastomer sealing members contact the external surface of drill pipe above said threaded connection, while said concave lower elastomer sealing members contact the external surface of drill pipe below said threaded connection. Elastomer strip sealing members contact the opposing, mating faces of the opposing semi-cylindrical half members.
During use, the mud bucket is suspended from a cable above a drilling rig floor, moved into position by rig personnel, and latched around the drill pipe in order to enclose a threaded connection. In most cases, a mud bucket is positioned and secured in this manner after mating threads of a threaded connection have been “broken-out”, but before said mating threads are completely disconnected and the adjoining pipe sections are separated. As such, after the mud bucket has been properly positioned latched in place, the upper pipe section is rotated to fully disconnect the threaded connection. Thereafter, said upper pipe section is axially lifted in order to separate it from the lower pipe section. With the mud bucket secured in place surrounding said threaded connection, drilling fluid flows out of the disconnected upper pipe section, into an interior chamber formed by the mud bucket, through the hose, and into the mud tank or other storage reservoir.
A significant problem with conventional mud bucket design is that said seals require a considerable amount of force in order to effectively seal against the external surface of the pipe sections. Additionally, rotation and axial translation of said pipe (which can have rough outer surfaces) through the seal members can cause abrasive wear and damage to the inner sealing surfaces of the seal members. In many cases, the elastomer sealing members cannot compensate for this wear, thereby causing said sealing members to leak. Likewise, the elastomer strip sealing member cannot compensate for wear or damage, and thus, said elastomer strip sealing member can also begin to leak. Generally, the elastomer seals are fastened to the mud bucket components via nuts and bolts and, thus, replacement of said seals can be inefficient and time consuming. Moreover, said nuts and bolts are subject to being lost or falling into a wellbore.
As a result, there is a need for a mud bucket that is relatively light-weight in order for said mud bucket to be safely moved and positioned along the rig floor; that comprises a means to compensate for wear to pipe sealing members; that can compensate for wear or damage to strip sealing members; that is easy to latch and unlatch; and, that comprises effective fluid sealing members that may be changed rapidly and easily without the removal of small components (such as, for example, nuts and bolts).